The Enhanced Lower parts kit offers a convenient upgrade package for the AR15 for those looking for a complete Strike Industries solution for new builds, or to update their plain jane AR. This kit includes bolt catch spring, buffer retainer spring, disconnector spring, hammer spring, magazine catch spring, pivot detent spring, selector spring, takedown detent spring, trigger spring, bolt catch plunger and roll pin, hammer pin, pivot detent, takedown detent, trigger pin, and a buffer retainer. The Enhanced parts included are a bolt catch, magazine catch, magazine catch button, pivot pin, takedown pin, two SI selector lever, SI selector end plate, and a SI 60-90 degree 3-in-1 selector shaft. The Enhanced Lower parts kit offers a convenient upgrade package for the AR-15 for those looking for a complete Strike Industries solution for new builds, or to update their plain jane AR. This kit includes all the basics that you will need to build out your AR (minus grip), but with Strike Industries Enhanced lower parts where applicable. Features: Includes SI's signature enhanced lower parts (AR-EBC, AR-SMC, AR-EPTP, & AR-HS-60/90-3in1) SI's trigger springs provide a consistent 4-1/2 to 5-1/2 lb trigger pull with our fire control group